fun main(args: Array<String>) {
    println(getAns())
}

fun getAns():Int {
    val n = readLine()!!
    if(n.first() != '1') {
        return -1
    }
    val tmp = n.drop(1)
    if(tmp.isEmpty()) {
        return -1
    }
    if(tmp.all { it == '3' }) {
        return tmp.length
    }
    return -1
}